Near IR emitting novel rhodanine-3-acetic acid based two donor-π-acceptor sensitizers for DSSC: Synthesis and application

Abstract

A series of metal-free novel organic dyes MR1, MR2, MR3 and MR4 containing N, N-diethylaniline as a donor group, rhodanine-3-acetic acid as an acceptor group separated by thiophene as a spacer were designed and synthesized. The detailed study of electrochemical, photophysical, photovoltaic and theoretical properties highlights their utilization in Dye-Sensitized Solar Cell (DSSCs) application. The sensitizers MR1, MR2, MR3 and MR4 show power conversion efficiencies (PCEs) of 3.51%, 2.58%, 6.56% and 6.32% respectively in DSSCs. Among the synthesized dyes, MR3 designed with thiophene ring as a π-linker with cyano (-CN) group in conjugation shows maximum PCE of 6.56%. The enhanced efficiency of sensitizer MR3 is due to extra electron withdrawing CN group which acts as an efficient electron trap. All these dyes were characterized by 1H NMR, 13C NMR and CHN analysis. Photophysical properties recorded in nine different solvents show positive solvatochromism and high Stokes shift.MR3 and MR4 emit in near IR region with large Stokes shift. The extensive density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculation show a good correlation between observed absorption and theoretical vertical excitation. Structural modification and its impact on absorption and photoconversion efficiency is established.